Well...
Well, I've never tried the Forbes methods. Best method is to (1) have top level card of particular airline and (2) ask nicely. Upgrades are often automatic on crowded routes on Swiss for Gold card holders, let alone Circle cards. Tel Aviv-Zurich is a great example.
Currently moving from one company to another by merger, I have to learn new tricks. Old complany had C-class policy, so upgrades to F were the trick. New company has "lowest Y" policy, so the first trick is C-class upgrades. Of course, I won't keep the top level cards (four airlines) for long at the lower fares, so I had better get moving. (SFO to Europe is a long, long trip with no sleep.
Of the five tried long haul, the best is Swiss, followed by BA, then Lufthansa and United, with Air France a long way behind. (Least comfortable beds, worst attitude, most strikes). In Business, I would say Virgin (Upper Class is a C/J-class fare, not an F fare), followed by BA (only on the flat bed seats, despite the rattles), Lufthansa (Best conventional seat for sleeping, video too small), Swiss (A330 only, MD-11 much inferior, both seats strangely difficult to sleep in), Air france seat recline does not allow sleep. TAP has least space, Alitalia OK. Rumour is that Aer Lingus Premier is really good, but never tried. KLM long haul business also has loads of space, but I have not tried it many years, so forget.
In long-haul economy, there is no contest. American has several inches more space than anyone else. Contest over, despite the food and service. Personally, my kids like the Swiss seatback videos though (A330 only).
Contrary to other views in this thread, US domestic F class is not the same as European C/J class, simply because the seating is normally 2+2 on single-aisle aircraft, and there is more legroom, and leather seats. It's sort of a C+. Three-class domestic still exists.
Momo